Hmm... it's difficult without the tell-tale details that we unconsciously pick up on when we guess someone's age. I've seen some 16-year olds who could look like this without my specs on (I mean me, not them) and some in their mid-thirties.

But I would hazard a guess at 27 and three quarters.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)